U.S. patent number 4,180,734 [Application Number 05/872,449] was granted by the patent office on 1979-12-25 for gas analyzer.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Andras Gedeon.
United States Patent |
4,180,734 |
Gedeon |
December 25, 1979 |
Gas analyzer
Abstract
An illustrative embodiment shows infrared radiation divided into
two beams which impinge on respective detectors via respective
stationary filters, so as to provide measures of two constituents
of a mixture of gases used for mixed anaesthesia. The same angled
mirrors which provide the measurement beams may also be reflective
on their sides toward the infrared source to provide reference
beams to the filters and detectors such that the detectors may
alternately sense the measurement and reference beams with the aid
of beam interrupters.
Inventors: |
Gedeon; Andras (Taby,
SE) |
Assignee: |
Siemens Aktiengesellschaft
(Berlin & Munich, DE)
|
Family
ID: |
6001615 |
Appl.
No.: |
05/872,449 |
Filed: |
January 26, 1978 |
Foreign Application Priority Data
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|
|
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Feb 18, 1977 [DE] |
|
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2707090 |
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Current U.S.
Class: |
250/345; 250/349;
250/373; 600/532 |
Current CPC
Class: |
G01N
21/3504 (20130101); A61B 5/083 (20130101) |
Current International
Class: |
A61B
5/08 (20060101); A61B 5/083 (20060101); G01N
21/35 (20060101); G01N 21/31 (20060101); G01J
001/00 (); G01J 001/42 () |
Field of
Search: |
;250/338,339,343,345,344,373,349 ;356/51,88,93,97 ;128/2C |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Smith; Alfred E.
Assistant Examiner: Fields; Carolyn E.
Attorney, Agent or Firm: Hill, Van Santen, Steadman, Chiara
& Simpson
Claims
I claim as my invention:
1. A gas analyzer having a respiratory tube through which the
respiratory gas flows for analysis, a radiation source which
radiates through the respiratory tube, radiation receiving means,
reflector means which direct the radiation onto the radiation
receiving means, and several radiation filters, each of which is
assigned to one gas, characterized in that the reflector means (14,
15, 16) are constructed and arranged so that the radiation is
divided into two beams of radiation (18, 19) each of which exits
through a window (20, 21, 20a, 21a), that the receiving means
comprises two radiation detectors (22, 23), each of which detects
one beam of radiation (18, 19) issuing from the respiratory tube
(5), and that the radiation filters (24, 25), each assigned to a
specific gas, are arranged in each case before a respective one of
the radiation detectors (22, 23), and further characterized in that
the reflector means comprises concave reflector means (14) disposed
opposite the radiation source (12), and two obliquely arranged
plane reflectors (15, 16) lying symmetrically at an angle to one
another opposite the concave reflector means (14), that a clearance
(17) is left between the plane reflectors (15, 16) through which
the radiation of the radiation source (12) is focused to a beam of
radiation striking the concave reflector means (14) and that the
angle of inclination of the plane reflectors (15, 16) is selected
so that they each reflect a portion of the beam of radiation after
reflection at the concave reflector means (14), in each case
through a window (20, 21).
2. A gas analyzer having a respiratory tube through which the
respiratory gas flows for analysis, a radiation source which
radiates through the respiratory tube, radiation receiving means,
reflector means which direct the radiation onto the radiation
receiving means, and several radiation filters, each of which is
assigned to one gas, characterized in that the reflector means (14,
15, 16) are constructed and arranged so that the radiation is
divided into two beams of radiation (18, 19) each of which exits
through a window (20, 21, 20a, 21a), that the receiving means
comprises two radiation detectors (22, 23), each of which detects
one beam of radiation (18, 19) issuing from the respiratory tube
(5), and that the radiation filters (24, 25), each assigned to a
specific gas, are arranged in each case before a respective one of
the radiation detectors (22, 23), and further characterized in that
the reflector means comprises concave reflector means (14) disposed
opposite the radiation source (12), and two obliquely arranged
plane reflectors (15, 16) lying symmetrically at an angle to one
another opposite the concave reflector means (14), that a clearance
(17) is left between the plane reflectors (15, 16) through which
the radiation of the radiation source (12) is focused to a beam of
radiation striking the concave reflector means (14) and that the
angle of inclination of the plane reflectorv (15, 16) is selected
so that they each reflect a portion of the beam of radiation after
reflection at the concave reflector means (14), in each case
through a window (20, 21), and further characterized in that the
obliquely arranged reflectors (15, 16) are reflective on both
sides, that the radiation of the radiation source (12) is also
aligned directly onto the side of the reflectors (15, 16) which is
facing the radiation source (12), and the reflectors (15, 16) are
aligned so that they direct this primary radiation in separate
beams of radiation (26, 27) via the filters (24, 25) onto the
detectors (22, 23) so that each detector (22, 23) is struck by a
beam of radiation (26, 27) via the assigned filter (24, 25), and
that a radiation interrupter (28, 29) is disposed before each
detector (22, 23) which alternately interrupts the two beams of
radiation (18, 19, and 26, 27) striking the detectors (22, 23).
Description
BACKGROUND OF THE INVENTION
The invention relates to a gas analyzer having a respiratory tube
through which the respiratory gas flows for analysis, a radiation
source radiating through the respiratory tube, reflectors which
direct the radiation onto radiation receiving means, and several
radiation filters, each of which is assigned to a gas.
At the present time halogenated hydrocarbons in gaseous form are
used routinely in mixed gases for mixed anaesthesia. Mixed
anaesthesia means that sleep is induced by a hypnotic, analgesia
(elimination of pain) by an analgesic and muscular relaxation by
means of a muscular relaxation agent. Mixed anaesthesia is used
frequently in modern hospital care. In practice, when this is
carried out the patient is given a gas mixture consisting of three
gases, for example oxygen, nitrous oxide, and in addition a
halogenated hydrocarbon. Thus the problem arises of measuring the
concentrations of the three gases.
A gas analyzer of the initially named kind is known from Canadian
Pat. No. 1,000,070. A radiopaque disc with cutout portions is
attached to a filter disc which is rotatable by means of a motor.
The parts of the filter visible in the cutout portions are
permeable with respect to various wave lengths of the received
radiation. A filter is assigned to each gas concentration to be
metered, which transmits those radiation components which are
absorbed by the gas to be measured. The filter portions can be
moved in front of a single radiation detector by means of an
electric motor which rotates the disc. This gas analyzer, which is
bulky and of complicated construction, can only measure different
gas concentrations consecutively. Also, it has a relatively high
power consumption because of the motor.
SUMMARY OF THE INVENTION
The underlying task of the invention is to devise a gas analyzer of
the initially named kind which is compact and of simple
construction, which is capable of measuring three gas
concentrations simultaneously and which has a low power
consumption.
According to the invention this task is solved in that the
reflectors of the gas analyzer are so constructed and arranged that
the radiation is split into two beams of radiation each of which
exits through a window, in that two radiation detectors are
present, each of which detects a beam of radiation issuing from the
respiratory tube and in that a radiation filter assigned to a
specific gas is arranged in each case before each radiation
detector. Firstly, two gas concentrations can be measured
simultaneously by the two detectors in connection with two filters
with different absorption capacities. If the gas to be tested is
made up of three constituents, the concentration of the third
constituent can then be calculated.
Further objects, features and advantages and details of the
invention will be apparent from the following disclosure of an
exemplary embodiment which is illustrated in the accompanying sheet
of drawings, and from the sub-claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a diagrammatic representation of a gas measuring
device for illustrating the invention; and
FIG. 2 shows a schematically represented gas analyzer according to
the invention.
DETAILED DESCRIPTION
FIG. 1 shows a flexible tubular connection 3 arranged between a
patient 1 and a respiratory apparatus 2, for example, an
anaesthesia apparatus. During the inhalation phase, the anaesthesia
apparatus 2 conducts respiratory gas to the patient 1 via the
flexible connection 3. A gas analyzer 4 is disposed in the flexible
connection 3 for analyzing the inhaled gases. A respiratory tube 5
which is associated with the gas analyzer 4 is arranged in a
detachable manner in a cutout portion 7 of the gas analyzer housing
6. Thus, the respiratory tube 5 may be removed and sterilized. The
gas analyzer 4 is connected via connection lines 9, 10 with an
indicator device 8 for indicating the gas concentrations to be
measured. During the exhalation phases the air flows through the
tube 11, the free end of which discharges into the atmosphere.
FIG. 2 illustrates a radiation source 12 which is formed by an
infrared radiating ceramic rod. The rays of the radiation source 12
are directed by means of a screen 13. A concave reflector 14 is
disposed opposite the radiation source 12. Two plane reflectors 15,
16 which are reflective on both sides are symmetrically fixed
opposite the concave reflector 14 at an angle to one another. A
clearance 17 is left free between the plane reflectors 15, 16
through which the radiation of the radiation source 12 is focused
to a beam of radiation striking the concave reflector 14. The angle
of inclination of the plane reflectors 15, 16 is selected so that
each of these receives in each case one portion of this beam of
radiation after reflection at the concave reflector 14 and reflects
it back to the concave reflector 14. In this way, two separate
beams of radiation 18, 19 are obtained which exit, after reflection
at the concave reflector 14, in each case through a window 20, 21,
20a, 21a in the wall of the respiratory tube 5 and the cutout
portion 7. Two radiation detectors 22, 23 are present in the
housing 6 of the gas analyzer 4, each of which detects one of the
beams of radiation 18, 19 issuing from the respiratory tube 5 via
the windows 20, 21, 20a, 21a respectively. In each case a radiation
filter 24, 25, assigned to a specific gas, is disposed before each
radiation detector 22, 23.
The obliquely arranged reflectors 15, 16 are reflective on both
sides. The radiation of the radiation source 12 is also aligned
directly onto the sides of the reflectors 15, 16 facing the
radiation source. The reflectors 15, 16 are aligned so that they
direct the primary radiation of the radiation source 12 in separate
beams of radiation 26, 27 onto the detectors 22, 23 via the filters
24, 25, so that in each case a detector 22, 23 is struck by a beam
of radiation 26, 27 via the assigned filter 24, 25. An electrically
driven radiation interrupter 28, 29 is arranged between each filter
24, 25 and the associated detector 22, 23 and it may be moved
periodically from the position marked by a solid line to the
position shown by a dotted line and vice versa and thus alternately
interrupts the two beams of radiation 18, 19 and 26, 27 striking
the detectors 22, 23. The detectors 22, 23 are connected via the
connection lines 9, 10 with the indicator device 8 which
electrically evaluates the signals of the detectors 22, 23 and
gives the reading of the two gas concentrations which correspond to
the filters 24, 25.
The walls of the cutout portion 7 and the respiratory tube 5 also
have windows 30 to 33 and 30a to 33a which allow the radiation of
the radiation source 12 to pass through at the required
locations.
FIG. 2 clearly shows that the respiratory tube 5 may be removed
easily from the cutout portion 7 and that the gas analyzer 4 thus
forms a unit distinct from the respiratory tube 5.
By way of example, FIG. 2 shows a housing 6 with a square cross
section cutout portion 7. The square cross section tube 5 slides
axially into the cutout portion 7, so that when tube 5 is in
assembled relation as shown in FIG. 2, the housing 6 provides a
lightproof chamber surrounding the tube 5. The infrared
transmissive windows at 20, 21, and 30-33 of tube 5 may seal the
tube 5 gas tight except for its flow communication with the
connecting tube 3 (as indicated by the dot-dash lines referenced by
the numeral 3 in FIG. 2). Cutout portion 7 is defined by a tubular
wall of square cross section surrounding tube 5 on its four sides
and provided with infrared transmissive windows 20a, 21a, 30a-33a,
aligned with the corresponding windows of tube 5 as shown in FIG.
2. In this case respiratory tube 5 is removable in an axial
direction from the cutout portion 7 of housing 6 for
sterilization.
It will be apparent that many modifications and variations may be
effected without departing from the scope of the novel concepts and
teachings of the present invention.
* * * * *